Practical Engineering: Concrete and Steel -- An Effective Partnership

Rebar in concrete foundation walls is
among the more misunderstood aspects
of light construction. Most builders
have a pretty good feel for the strength
of framed walls and floors, but their
intuition deserts them when it comes
to the foundation. In consequence,
there is a lot of folklore about what
works and what doesn't.
Let's start with fundamentals. The
strength of concrete is in compression
— it easily resists direct crushing loads.
However, this marvelous quality is offset
by an extremely low strength in tension,
which gives concrete a tendency
to crack in service.
Concrete, depending on the mix,
will take a 2,500- to 8,000-pound-persquare-
inch load in compression. But in
tension, concrete will resist only about
250 to 350